Currently there are tens of thousands of depleted oil and natural gas wells around the world, which collectively possess significant amounts of petroleum resources that cannot currently be extracted using conventional extraction techniques.
For example, in a typical oil well, only about 30% of the underground oil is recovered during initial drilling (“primary recovery”). An additional approximately 20% may be accessed by “secondary recovery” techniques such as water flooding. In recent years, “tertiary recovery” (also known as “Enhanced Oil Recovery” or EOR) techniques have been developed to recover additional oil from depleted wells. Such tertiary recovery techniques include thermal recovery, chemical injection, and gas injection. Using current methods, these tertiary techniques allow for an additional 20% or more of the oil to be recovered.
Gas injection is one of the most common EOR techniques. In particular, carbon dioxide (CO2) injection into depleted oil wells has received considerable attention owing to its ability to mix with crude oil. Since the crude oil is miscible with CO2, injection of CO2 renders the oil substantially less viscous and more readily extractable.
Despite the potential advantages of CO2 in enhanced recovery, its use has been hampered by several factors. For instance, in order for the enhanced recovery process to be economically viable, the CO2 gas must be naturally available in copious supplies at reasonable cost at or near the site of the oil well. Alternatively, CO2 can be produced from industrial applications such as natural gas processing, fertilizer, ethanol and hydrogen plants where naturally occurring CO2 reservoirs are not available. The CO2 must then be transported over large distances via pipeline and injected at the well site. Unfortunately, such CO2 pipelines are difficult and costly to construct. Additionally, many oil sites are out of reach from such natural and industrial sources of CO2.
Another gas that can potentially be used for enhanced recovery purposes is hydrogen. Hydrogen has received considerably less attention than CO2, however. Hydrogen, although somewhat soluble with oil, is believed less so than CO2. Moreover, traditionally, hydrogen has been costly to produce and its use has not been justified from an economic standpoint.
The rising cost of crude oil, as high as $60 to $70 per barrel in recent times, has increased interest in new enhanced oil recovery technologies. Simultaneously, the low cost of coal, often lower than $30 per ton, has made coal an attractive fuel source for EOR purposes.
Accordingly, as recognized by the present inventors, what are needed are a novel method, apparatus, and system for extracting oil/petroleum from the ground or from oil wells, such as depleted oil wells, by utilizing driver gases generated from a coal source. What are also needed are a method, apparatus, and system for extracting natural gas from the ground or from natural gas wells by utilizing driver gases generated from a coal source.
Therefore, it would be an advancement in the state of the art to provide an apparatus, system, and method for generating large quantities of carbon dioxide, hydrogen and other gases from coal or a derivative of coal at low cost at or near an oil site.
It is against this background that various embodiments of the present invention were developed.